The AJKJS-9 monoclonal antibody reacts with the mouse ROR (t) protein. ROR is a member of the retinoic acid-related orphan receptor (ROR) family, which also includes ROR and ROR . ROR family proteins are ligand-dependent transcription factors that play roles in multiple physiological processes. ROR is expressed in several tissues including liver, lung, muscle, heart and kidney. Furthermore, it was discovered that alternative transcription results in the expression of an isoform, ROR t, which is expressed exclusively in cells of the lymphoid compartment, namely CD4+CD8+ “double-positive” thymoyctes, Th17 cells of the periphery and lymphoid tissue inducer (Lti) cells of lymphoid organs. The ROR t isoform differs from ROR by three unique amino acids at its amino terminus. Therefore, the AFKJS-9 antibody will react with both the ROR and ROR t isoforms.